This application seeks support for a conference on the chemical modifications of the biological effects of radiation and chemotherapy agents. The meeting is planned for mid-September 1981 at Key Biscayne, Florida, or a similar location. Attention will focus on - a) hypoxic-mediated drugs which act as sensitizers of radiation and which have more recently been shown to enhance the cytotoxic action of chemotherapy agents. b) Protectors which differentially protect normal tissues relative to tumors from the effects of radiation and chemotherapy agents. The development of the electron affinic compounds has been facilitated by close cooperation between chemists, biologists, and clinicians; research in this area has moved from the petri dish to the clinic in a remarkably short time. Protectors are likely to progress just as quickly. The proposed meeting will foster the further application to basic scientific knowledge to clinical radiation oncolgy and medical oncology. The program will include topics ranging from the synthesis of new drugs, the addressing of basic mechanism, reporting of clinical trials. The previous meeting on this topic was held at Key Biscayne in October 1979; the field is progressing so rapidly that another meeting two years later is considered imperative. A development of considerable importance since the last meeting has been the discovery that hypoxic-mediated drugs potentiate chemotherapy agents as well as radiation; this greatly expands the scope of their potential use.